Reproductive trade-offs in benthic decapod crustaceans of high southern latitudes: tolerance of cold and food limitation
Caridean shrimps comprise the only decapod infraorder in the markedly impoverished high Antarctic decapod fauna. Their presence, with about a dozen species only, was previously assigned to their capability of down-regulating high haemolymph magnesium ([Mg2+]HL) concentrations at low temperatures. Th...
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| Format: | Thesis |
| Language: | unknown |
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2003
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| Online Access: | https://epic.awi.de/id/eprint/8570/ https://hdl.handle.net/10013/epic.19096 |
| Summary: | Caridean shrimps comprise the only decapod infraorder in the markedly impoverished high Antarctic decapod fauna. Their presence, with about a dozen species only, was previously assigned to their capability of down-regulating high haemolymph magnesium ([Mg2+]HL) concentrations at low temperatures. This regulation is missing or insufficient in reptant decapods, affecting in particular their scope of activity. This deficiency has been hypothesised as one important factor explaining their extinction during Antarctic cooling in the Tertiary, as evidenced by the fossil record.The present work demonstrates an ecological adaptation in the early life history of decapods to ecophysiological constraints in the cold, primarily a mismatch between reproductive traits and a marked seasonality of primary production and low temperatures increasing with latitude. It is shown that on a macroecological scale, natant decapods show remarkable plasticity in changing their early life history patterns with latitude and decreasing water temperature. These changes include, for example, an increase in egg size, hatching of large and advanced larvae and a reduction of fecundity with latitude. Energy saving traits to abbreviate larval developments such as a strong suppression of the number of instars, low metabolic losses in very thin exuviae during fewer moults, and a loss of highly variable developmental pathways compared to lower latitides, are observed already in the Subantarctic realm of southernmost America. Early larvae generally present a high resistance to starvation, which in combination with an abbreviated larval development allows for a better synchronisation with peaks in food availability. However, caridean larvae rely on primary production, and the evolutionary step towards complete endotrophic larval development, possibly due to phylogenetic constraint, is almost unknown in marine shrimps.The need for food in planktotrophic and extended larval development of ancestor reptants, and the lacking resistance of larvae to ... |
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